Returned to WebAssist HTML Editor page (logged in) and paid for the DW extension via PayPal.

So, while PP are NOT my favorite people these days, that shows one good reason to have a spare?? PP WPS seller account (free) lying around.

Outcome: WA gateway payments have issues with some perfectly good cards. If that was fixed no one would need to go through all this although it took less than a half hour with an existing PP seller account.